Process for recovering tin



p 1 1939- Y I J. o. BETTERTON ET AL 2,173,263

PRocEss FOR RECOVERING TIN.

Filed Dec; 3, 1955 INVENTORS Jesse a Belieflan Yurii 1S. [Made f wbiiw Patented Sept. 19, 1939 PROCESS FOR RECOVERING TIN Jesse 0. Betterton and Yurii E. Lebedefi,

Metuchen, N. J., assignors to American Smelt-ff ing and Refining Company, New York, N." Y., a corporation of New Jersey Application December 2, 1935, Serial No. 52,450

7 Claims.

This invention relates to the metallurgy of tin and provides an improved electrochemical process for recovering metallic tin from stannic chlo ride.

In treating Secondary metals containing tin, such as impure solder and other tin alloys, the tin may be separated by chloridization, e. g. by reaction of the molten alloy with chlorine gas thereby converting the tin to tin tetrachloride, which is volatile at the temperatures employed and is readily recovered by condensation.

By the process of the present invention tin is precipitated from an aqueous stannic chloride electrolyte in a galvanic cell equipped with electrodes of dissimilar materials and is recovered in a form readily amenable to melting down to pig metal.

In accordance with the invention, the electrolyte is placed in-a cell equipped with a cathode whichis-electronegative with respect to tin, e. g., copper or mercury and a soluble anode which is electropositive with respect to tin, e. g., zinc or aluminum. Suitable electrical connection between anode and cathode are provided to yield a shorted cell.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, asto its objects and advantages, and the manner in which it may be carried out, may be better understood by referring to the following description, taken in con nection with the accompanying drawing forming a part thereof, in which Fig. 1 is a plan view of one type of cell suitable work 16 within which are zinc plate l8 and zinc rods or strips 20 and zinc scrap 22. If desired plate I8 and rods 20 may be of other conductive material such as graphite so long as care is exercised in seeing that there is good contact between] them and the zinc or equivalent. ,anodic metal which is electropositive with respect to tin. The cathode 24 which isof copper or equivalentmetal opening l2. which will not enter into solution in the preschloride which comprises adding sufiicient water i to the stannic chloride to produce an electrolyte anode, electrically connecting the anode and electronegative to tin is connected with the anode by wires 26 thereby preventing accumulation of precipitated tin on the electropositive metal of the anode. The level of the stannic chloride electrolyte in tank In is indicated at 28.

In operation the scrap zinc rapidly dissolves and the tin deposits at the cathode 24 from which it falls to the bottom of the tank l0- collecting as a sludge 30 and is removed via the clean-out The impurities in the scrap zinc ence of an excess of zinc are, retained within the permeable anode compartment and are thereby prevented from contaminating the precipitated tin. The tin is withdrawn from the tank and appropriately melted down and cast.

The following specific example will serve to illustrate the invention: to volumes of stannic chloride having a specific gravity of 2.28 and analyzing 45.5% (103.7 parts by weight) tin, there were added volumes of water which gave a clear solution of tin tetrachloride. Care was used in adding the water in view of its vigorous reaction with stannic chloride.

The aqueous stannic chloride electrolyte was placed in a cell such as heretofore has been described and illustrated in the drawing. An excess of some 200 partsby weight of zinc scrap was provided in the anode compartment. Solutionof the zinc was rapidlyeffected and the tin deposited at the cathode settled quicklyto the bottom of the tank.

The tin sludge was put through a filter press and the filter cake slowly dried. The filtrate (138 volumes) analyzed only 4.8 grams of tin 35 metal electropositive to tinasan anode and a metal electronegative to tin a'sthe cathode. env closingthe said anode jin 'a permeable diaphragm for retaining solid material's separated from the cathode to form a shorted cell and allowing the tin to precipitate at the cathode as a sludge.

2. The process for producing tin from stannic chloride which comprises preparing an aqueous solution of the stannic chloride utilizing said solution as the electrolyte in an electrochemical cell having an anode comprising a metal electropositive to tin and a cathode electronegative to tin electrically connecting the anode and cathode to form a shorted cell, and recovering the precipitated tin.

3. The-process for treating secondary metals containing tin which comprises converting the tin to stannic chloride, preparing an aqueous solution of the stannic chloride, utilizing said solution as the electrolyte in an electrochemical cell having an anode comprising zinc and a cathode electronegative to tin electrically connecting the anode and cathode to forma shorted cell, and recovering the tin which deposits from the electrolyte at the cathode.

4. The process for treating secondary metals containing tin which comprises converting the tin to stannic chloride, preparing an aqueous solution of the stannic chloride, utilizing said solution as the electrolyte in an electrochemical cell equipped with an anode comprising a metal which will enter the electrolyte and displace tin therein and a cathode electronegative to tin, said anode and cathode being separated by a permeable diaphragm electrically connecting the anode with the cathode to form a shorted cell, and recovering the tin which is precipitated fromthe electrolyte by the action of the cell.

5. The process for treating secondary metals containing tin which comprises converting the tin to stannic chloride, preparing an aqueous solution of the stannic chloride, utilizing said solution asthe electrolyte in an electrochemical cell equipped with an anode comprising zinc and a cathode electronegative to tin, said anode and cathode being separated by a permeable diaphragm, electrically connecting the anode with the cathode to form a shorted cell, and recovering the tin which is precipitated from the electrolyte by the action of the cell.

6. The process for recovering tin from stannic chloride which comprises adding sufflcient water to the stannic chloride to produce an electrolyte therefrom while avoiding production of solid products of hydrolysis, placing the resulting electrolyte into an electrochemical cell including a zinc anode and a metal electronegative to tin as the cathode, enclosing the said anode in a permeable diaphragm for retaining solid materials separated from the anode, electrically connecting the anode and cathode to form a shorted cell and allowing the tin to precipitate at the cathode-as a sludge.

7. The process for recovering tin from stannic chloride which comprises adding suflicient water to the stannic chloride to produce an electrolyte therefrom while avoiding production of solid products of hydrolysis, placing the resulting JESSE O. B I'ERTON. YURII E. 

